Hi everyone! I have a lab assignment due on Monday and I am lost with it completely, if you can, just tell me what it wants from me:

 

Assignment: Write an SOP for the production of 100 ml of the following buffer:

Recipe:

10mM Tris-HCL at pH 7.5

150 mM NaCl

2 mM EDTA

1% SDS

 

What do I need to calculate? does it want equal grams of each in 100 ml? Ehm.. I'm looking into information I have, trying to figure out how to use it, but the thing is that I don't have the final molarity, and how can I get the grams of each component, if I have only Molarity in recipe and formula weights? it's gonna give me gms/L, not grams, coz I don't have the volumes.

 

SOP is standard operation procedure, a method to make it.

 

Oh, help me out with this, please.

You need to work out how much of each component you need to have to make that buffer so that it has the required concentrations. The SDS would be the easiest place to start - you either need 1g (if its % weight/volume) or 1ml (if its % vol/vol) as a 1% solution is 1g (or 1ml) per 100ml.

 

The NaCl and EDTA are pretty straight forward as well. Once you get the g/L figure just divide it by 10 to give g/100ml. The tris-HCl is a bit more complex as you need to use the Henderson-Hasselbach equation, pH=pKa + log([base]/[acid], and then buffer concentration = [acid] + [base].

for a quick overview see http://www.haverford.edu/chem/Scarrow/GenChem/acidbase/buffer_prep.html

and for more detail http://www.emdbiosciences.com/SharedImages/Calbiochem/Calbiochem_Buffers_Booklet_CB0052_E.pdf

 

Hope this helps